Coordination chemistry of [2 + 2] Schiff-base macrocycles derived from the dianilines [(2-NH2C6H4)2X] (X = CH2CH2, O): structural studies and ROP capability towards cyclic esters

Wang, Kuiyuan; Prior, Timothy J.; Hughes, David L; Arbaoui, Abdessamad; Redshaw, Carl

Abstract

Reaction of the [2 + 2] Schiff-base macrocycles {[2-(OH)-5-(R)-C6H2-1,3-(CH)2][CH2CH2(2-C6H4N)2]}2(R = Me, L1H2;tBu, L2H2) with FeBr2afforded the complexes [FeBr(L1H2)]2[(FeBr3)2O]·2MeCN (1·2MeCN), [FeBr(L2H2)][X] (X = 0.5(FeBr3)2O,2·0.5MeCN, X = Br,3·5.5MeCN), respectively. Reaction of L2H2with [KFe(OtBu)3(THF)] (formedin situfrom FeBr2and KOtBu), following work-up, led to the isolation of the complex [Fe(L2)(L2H)]·3MeCN (4·3MeCN), whilst with [CuBr2] afforded [CuBr(L2H2)][CuBr2]·2MeCN (5·2MeCN). Attempts to form mixed Co/Ti species by reaction of [CoBrL2][CoBr3(NCMe)] with TiCl4resulted in [L2H4][CoBr4]·2MeCN (6·2MeCN). Use of the related oxy-bridged Schiff-base macrocycles {[2-(OH)-5-(R)-C6H2-1,3-(CH)2][O(2-C6H4N)2]}2(R = Me, L3H2;tBu, L4H2) with CoBr2led to the isolation of the complexes [(CoBr)2(L3)]·2C3H6O (7·2C3H6O), [Co(NCMe)2(L4H2)][CoBr4]·5MeCN (8·5MeCN), [Co(NCMe)6][CoBr3(MeCN)]2·2MeCN (9·2MeCN). For comparative structural/polymerisation studies, the complexes {CoBr(NCMe)L5}2·2MeCN (10·2MeCN) and [Co(NCMe)2L5]2[CoBr3(NCMe)]2(11), [FeBr(NCMe)L5]2·2MeCN (12·2MeCN) where L5H = 2,6-(CHO)2-4-tBu-C6H2OH, as well as the chelate-free salt [Fe(NCMe)6][FeBr3OFeBr3] (13) have been isolated and structurally characterized. The ability of these complexes to act as catalysts for the ring opening polymerisation (ROP) of ε-caprolactone (ε-CL) and δ-valerolactone (δ-VL) was investigated, as well as co-polymerisation of ε-CL withrac-lactide (r-LA) andvice versa.

Citation

Wang, K., Prior, T. J., Hughes, D. L., Arbaoui, A., & Redshaw, C. (2021). Coordination chemistry of [2 + 2] Schiff-base macrocycles derived from the dianilines [(2-NH2C6H4)2X] (X = CH2CH2, O): structural studies and ROP capability towards cyclic esters. Dalton Transactions : an international journal of inorganic chemistry, 50(23), 8057-8069. https://doi.org/10.1039/d1dt00711d

• Journal Article Type: Article
• Acceptance Date: May 4, 2021
• Online Publication Date: May 4, 2021
• Publication Date: Jun 21, 2021
• Deposit Date: May 10, 2021
• Publicly Available Date: May 10, 2021
• Journal: Dalton Transactions
• Print ISSN: 1477-9226
• Electronic ISSN: 1477-9234
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 50
• Issue: 23
• Pages: 8057-8069
• DOI: https://doi.org/10.1039/d1dt00711d
• Keywords: Schiff-base; Macrocycle; Iron; Cobalt; Copper; Structures; Ring opening polymerisation
• Public URL: https://hull-repository.worktribe.com/output/3767567